As sound generation devices used in electronic products such as mobile phones, televisions, and computers, speakers are widely applied in people's daily production and life. At present, common speakers mainly comprise moving-coil speakers, electromagnetic speakers, capacitive speakers, piezoelectric speakers, and the like. The moving-coil speakers are widely applied because of the characteristics such as relatively simple fabrication, low costs, and desirable low-frequency sound generation advantages.
An existing moving-coil speaker usually comprises a speaker module housing and a speaker unit. A typical structure of the speaker unit comprises a vibration system, a magnetic circuit system, and an auxiliary system. The auxiliary system usually comprises a housing that can accommodate the vibration system and the magnetic circuit system. The vibration system comprises a vibration diaphragm, a vibration voice coil fixed on a side of the vibration diaphragm, and a dome (rounded roof portion) fixed at the center position of the vibration diaphragm. The magnetic circuit system comprises a frame and a magnet and a washer that are fixed on the frame.
To improve the acoustic performance of a speaker and prevent a speaker from damages, smart PAs (smart power amplifiers) are increasingly applied to the field of speakers. A smart PA increases an output voltage output to a vibration voice coil to increase a vibration displacement of a vibration diaphragm, and a waveform returned by the vibration voice coil can be monitored. In an algorithm processing mechanism, the output voltage output to the vibration voice coil is analyzed and adjusted according to the waveform of an electrical signal, so as to achieve the objective of protecting the vibration diaphragm while increasing the volume of a speaker. In particular, to prevent a voltage value output by the smart PA from becoming excessively large to cause an excessively large vibration displacement of the vibration diaphragm, an upper limit value of the output voltage is preset in the algorithm processing mechanism of the smart PA. The algorithm processing mechanism ensures that the vibration displacement of the vibration diaphragm under the effect of the output voltage output to the vibration voice coil remains less than a preset safe displacement. In this method, an actual value of the vibration displacement of the vibration diaphragm is not used, so that an actual vibration displacement of the vibration diaphragm may be less than or even greater than an amplitude of the vibration diaphragm. As a result, the performance of the vibration diaphragm cannot be maximized, and the acoustic performance of a speaker is directly affected. Moreover, when an actual displacement is excessively large and fails to be effectively recognized by using this method, the vibration diaphragm may also fail, and the speaker may consequently fail.